The extermination under our noses
Voracious killer wasps are causing some of New Zealand’s native bugs to go extinct, insect experts believe.
Wasps are a serious problem for people on picnics, but their effects on native insect populations are devastating.
The lifespan of native insects in wasp-dense areas can be a matter of hours, and native species may even have been driven extinct.
Victoria University insect ecologist Professor Phil Lester says he was ‘‘sure’’ there have been local extinctions.
‘‘There must have been at least local extinctions of species, things like the forest ringlet butterfly that we just don’t see many of anymore,’’ he says.
The more wasps, the worse the effects they have on the ecosystem, and Lester says this year is looking like it’s going to be a ‘‘bumper year for wasps,’’ thanks to the hot, dry spring.
Last year, The Nelson Mail and Stuff launched a community campaign to wipe out wasps.
With help from the Department of Conservation (DOC), the community, and other conservation groups, the Wasp Wipeout campaign raised over $50,000 and saw a 98 per cent reduction in wasp populations.
Hundreds of volunteers set Vespex bait traps along hundreds of kilometres of DOC walking tracks and public areas, and this year the programe is expanding into a nationwide effort.
Wasps have a very high requirement for protein in their diet, and their primary source is other insects.
University of Auckland Associate Professor Jacqueline Beggs ran a study to determine the effects that wasps have on their fellow invertebrates by placing labreared spiders and caterpillars into wasp-dense areas and timing how long they lasted.
‘‘In some cases you barely put the jolly thing on the plant and whoosh - it was gone,’’ she says.
Beggs found the majority of the prey insects were gone within the first half hour, and from her data calculated that the chances of those insects surviving to reproduce in high wasp years were ‘‘next to zero’’.
Some of the flow-on effects of this are obvious, and still more effects are happening on a scale that most people won’t notice.
Birds are not only out-competed for the honeydew wasps greedily guzzle down, they are also outcompeted for the insects they might snack on.
Lester says many people told him about the changes in birds’ habits depending on the number of wasps.
‘‘People in Lake Rotoiti that supplementary-feed birds with sugar-water tell me when there’s a high number of wasps the birds are hungry, but when people come and use Vespex you don’t see nearly as many birds at the supplementary feeders,’’ he says.
Wasps are generalised and opportunistic feeders. They don’t target any particular insects - rather, they eat them all, starting with the big ones and working their way down.
‘‘Then they just start eating smaller and smaller things, so by the end of a high-density wasp season I’ve seen them eating little sandflies off the windows of huts. They’re scraping the bottom of the barrel, and your heart just sinks, you think ‘oh no, that just means they’ve eaten everything else’.’’
While there is no documentation to show that wasps have been directly responsible for local extinctions, Beggs says regardless, the damage they do to ecosystems should not be underestimated.